Journal
ECOLOGY
Volume 102, Issue 3, Pages -Publisher
WILEY
DOI: 10.1002/ecy.3250
Keywords
herbivory; insects; jasmonic acid; plant defense; physical defense; silica; silicon
Categories
Funding
- Australian Research Council [FT170100342, DP170102278]
- Australian Research Council [FT170100342] Funding Source: Australian Research Council
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Plants deploy chemical and physical defenses against arthropod herbivores, with silicon playing a crucial role in these defenses. Silicon enrichment in plants can lower JA induction levels and induce physical defenses, negatively impacting chewing herbivores. These silicon-based defenses are herbivore-specific and more effective against chewing herbivores compared to fluid feeders.
Plants deploy an arsenal of chemical and physical defenses against arthropod herbivores, but it may be most cost efficient to produce these only when attacked. Herbivory activates complex signaling pathways involving several phytohormones, including jasmonic acid (JA), which regulate production of defensive compounds. The Poaceae also have the capacity to take up large amounts of silicon (Si), which accumulates in plant tissues. Si accumulation has antiherbivore properties, but it is poorly understood how Si defenses relate to defense hormone signaling. Here we show that Si enrichment causes the model grass Brachypodium distachyon to show lower levels of JA induction when attacked by chewing herbivores. Triggering this hormone even at lower concentrations, however, prompts Si uptake and physical defenses (e.g., leaf hairs), which negatively impact chewing herbivores. Removal of leaf hairs restored performance. Crucially, activation of such Si-based defense is herbivore-specific and occurred only in response to chewing and not fluid-feeding (aphid) herbivores. This aligned with our meta-analysis of 88 studies that showed Si defenses were more effective against chewing herbivores than fluid feeders. Our results suggest integration between herbivore defenses in a model Si-accumulating plant, which potentially allows it to avoid unnecessary activation of other costly defenses.
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